1. Field of the Invention
The present invention relates to an apparatus for recording or retrieving data on a magnetic tape.
2. Description of Related Art
The prevailing apparatus for recording or retrieving data on a magnetic tape (hereinafter referred to simply as “tape”), known in the art, typically includes a magnetic head (hereinafter referred to simply as “head”) for recording (writing; encoding) or retrieving (reading; decoding) data on the tape, and a transport unit for driving (moving) the tape past the head. The apparatus of this type is designed to require a tape to run at speeds higher than a predetermined threshold value during the operation of writing or reading data so that an adequate clearance is kept between the tape and the head as if the tape is supported by air bearing. However, during a tape accelerating/decelerating period, e.g., periods of transition between a standstill and a normal running state, the running speeds (transport speeds) of the tape become lower than the speed of the normal tape running period, and thus a sufficient clearance cannot be kept, with the result that the tape and the head are brought into contact with each other and slid with an increased frictional resistance such that the tape would likely stick to the head in some circumstances.
Meanwhile, a technique known in the art (e.g., as disclosed in JP 6-28635 A) has proposed that a head be ultrasonically vibrated all the time in a direction of travel of a tape. In this technique, as disclosed, the object of ultrasonic vibrations of the head is to suppress sticking of magnetic powder to the head; however, the ultrasonic vibrations of the head may be expected to prevent sticking of the tape to the head.
However, the above technique in which the head is ultrasonically vibrated all the time would possibly induce disadvantageous phenomena when adapted to a magnetic tape that is recorded with high recording density, for example, in that: (1) the head could drift out from an appropriate recording or retrieving position (“off track”); (2) that a clearance between the head and the tape would become too wide (“spacing loss”).
The present invention has been made in an attempt to eliminate the above disadvantages. Illustrative, non-limiting embodiments of the present invention overcome the above disadvantages and other disadvantages not described above. Also, the present invention is not required to overcome the disadvantages described above, and illustrative, non-limiting embodiments of the present invention may not overcome any of the problems described above.